Firms collaborate on environmental management issues for number of reasons, including cost reduction, risk sharing and managing competition. Industrial symbiosis represents a voluntary collaborative approach among firms in geographic proximity. Companies participating in industrial symbiosis have been found to improve their individual economic and environmental performance, while the regions where they are located are thought to benefit through enhanced environmental quality. However, too few studies have actually investigated whether this is always the case. This paper considers a single case on the island of Puerto Rico, where several firms in a predominantly pharmaceutical manufacturing cluster participated in symbiosis initiatives for several decades. It examines whether early stage symbiotic activities, specifically a shared utility, met technical performance and community expectations for improved environmental quality. Results suggest that collaboration does not necessarily lead to expected environmental performance goals. The paper details the circumstances that led to under-performance of the initiative and the lessons for symbiosis projects in general. Copyright © 2010 John Wiley & Sons, Ltd and ERP Environment.